1. Field of the Invention
This invention relates generally to latches for hoist hooks and, more particularly, to a radio-controlled gravity latch assembly for a hoist hook.
2. Description of the Prior Art
In various construction and industrial applications, hoist hooks having some type of latch assembly are used to move large, heavy loads from one location to another. Generally, a latch located across the throat of the hook is manually retracted to open the throat of the hook and a bail or choker attached to the load is slipped on to the hook. The latch is then manually replaced to its original position to close the throat of the hook thus preventing the load from accidentally slipping off of the hook during transit. In normal circumstances, at least one and frequently two workmen are required to retract the latch from the hook throat and position the bail on the hook. Further, once the load has been moved to a new position, at least one workman is required to walk up to the hook and manually retract the latch to allow the load to be released. Thus, the attachment and release of the load to the hook pose safety hazards for workers who must manually open and close the latch to allow the load to be attached or released. In addition to the problem of personnel safety, a considerable amount of man-hours is lost by requiring workers to perform these duties manually.
An example of a typical prior art gravity-biased hook latch is shown in U.S. Pat. No. 1,525,292 to Greve. The Greve patent discloses a hook having a gravity latch pivotally located in the hook throat. The gravity latch has triangular-shaped sides and is pivotally mounted on the hook shank above the throat of the hook. The latch is normally biased in the closed position but can be manually retracted by a pair of handles.
To overcome the above-described shortcomings of manual latch assemblies, remote-controlled latches have been developed. U.S. Pat. No. 4,416,480 to Moody discloses a remote-controlled pneumatic release device for a rotatable hook. The hook is normally retained in a load carrying position by a latch pin engaged in a recess in an upper portion of the hook. A radio receiver, batteries, switch and solenoid valve are carried in a module located above the releasing hook. A signal from a portable radio transmitter is received by the radio receiver to close the switch and energize the solenoid valve. Actuation of the solenoid valve causes transmission of compressed air to the underside of the latch pin thus disengaging the latch pin from the hook and allowing the hook to rotate and release the load.
U.S. Pat. No. 4,073,531 to Androski discloses a radio-controlled safety hook assembly having a rotatable hook carried on a frame member. A battery, radio receiver, relay switch and motor gear assembly are located in a casing above the hook. A radio frequency from a portable transmitter is transmitted to the receiver which energizes the relay and actuates the motor. The motor turns a worm gear assembly which releases a safety latch and causes the hook to pivotally rotate to an open position. However, if power is lost while the hook is in the open position, it will remain open and must be manually closed. Other examples of hook latches and remote operators are disclosed in U.S. Pat. Nos. 1,062,084; 1,524,761; 1,576,197; 3,575,458; 4,195,872; 4,691,584; and 5,108,139.
The radio-controlled latch assemblies of the prior art are generally large, bulky, complex rotating hook arrangements which are difficult to manufacture and operate. Further, many of these prior art radio-controlled latch assemblies are difficult if not impossible to operate manually should they experience a loss of power. In addition, these prior art radio-controlled latch assemblies are generally not capable of being adapted for use with standard hoisting hooks.
Therefore, it is an object of the present invention to provide a compact, less complicated and more reliable radio-controlled latch assembly for engagement and disengagement of loads from hoisting hooks. Another object of the invention is to provide a radio-controlled latch assembly which, upon loss of electrical power, can still be easily and efficiently operated manually. A further object of the invention is to provide a radio-controlled latch assembly which can be easily installed and removed as a unit from a hoist hook.